Abstract

Epidemiological data suggest a positive relationship between increased calcium intake and decreased fat and total body mass in healthy people (McCarron et al. 1984, Davies et al., 2000). An in-vitro model suggesting the role of cyclic Adenosine Monophosphate (cAMP) and phosphodiesterase 3B (PDE 3B) has been implicated in the relationship between calcium and lipolysis (Xue et al., 2001). The objective of the series of studies presented in this thesis was to investigate the ergogenicity of supplementary calcium in endurance exercise via studying its influence on substrate metabolism and body composition.Study 1 examined the effects of four weeks of calcium (citrate) supplementation (1000 mg elemental calcium/day) on 60 minutes of cycling at a submaximal intensity of 50%Wpeak. The results of this study indicated that calcium supplementation significantly improved body composition of the participants with a greater fat loss and increased lean mass observed in highly trained athletes as compared to the recreationally trained participants. In addition, four weeks of calcium supplementation also showed an enhanced trend of availability of fatty substrates in the plasma and consequently an increased trend towards higher fat oxidation during submaximal exercise.Study 2 and 3 thus examined the effects of calcium supplementation directly on performance during endurance events (25 and 10 mile cycling time trials (TT)) in highly trained athletes. Results from these studies indicate that following calcium supplementation there was a meaningful improvement in power output (PO) (~4%) during the 25TT and ~2.7% in 10TT with corresponding better completion times in both the time trials. This amounts to an increase in ~2-3% higher PO%peak and ~3-5% increase in power output at lactate threshold, with the higher percentages attributable to the 25TT and the lower end to the 10TT. This increase in PO was achieved without the corresponding increase in oxygen consumption, thus significantly improving the gross efficiency of the cyclists. In addition, four weeks of calcium supplementation once again exhibited the same trends in body composition as observed in study 1 of decreased fat mass and a concurrent increase in lean mass. The results from this set of investigation indicate that calcium plays a multifactorial role in performance enhancement of endurance events. This may have been achieved via a combination of influence on substrate metabolism and body composition. The impact of calcium on fatigue mechanisms and vascular tone may have also played a part in increasing PO and thus efficiency of the athletes. Thus the potential of calcium to enhance performance needs further investigation in studies with larger sample sizes and different training status of athletes.